It is well known that one of the most dangerous hypertensive conditions is renal hypertension arising from renal insufficiency which is characterized, on the one hand, by constriction of the blood vessels of kidney and, on the other hand, according to recent investigations, by a decreased prostaglandin content of blood vessel walls of the kidney (Circ. Res. 36-37, Suppl. I, pp. 68 and 81, 1975) which is closely related to the process of constriction of the blood vessels of kidney.